Proximity-based service (ProSe) direct communication in the third generation partnership project (3GPP) standards refers to a mode in which user equipments (UE) can directly communicate with each other. ProSe direct communication may include, for example, device-to-device (D2D) communication and vehicle-to-related entity communication (V2X communication, which may include, for example vehicle-to-vehicle (V2V) communication, vehicle-to-infrastructure (V2I) communication and vehicle-to-pedestrian (V2P) communication). As shown in a schematic diagram in FIG. 14, a link between UE1 and UE2 between which a proximity-based service direct communication is performed is referred to as a sidelink. UE1 and UE2 are connected together via a PC5 interface, and UE1 and UE2 are connected to a base station via a Uu interface.
In addition, according to existing standards, in a case of a radio resource control (RRC) connection, an evolved base station (eNB) schedules a UE to perform a ProSe direct communication on the same resource as a major frequency of cellular communication between the UE and the eNB. Further, a UE that is RRC connected to other cell can also perform a ProSe direct communication based on a radio communication resource, such as a resource pool broadcasted on a public safety ProSe carrier, detected by the UE.